1. Field of the Invention
The present invention relates to a liquid crystal display (LCD), and more particularly, to a stripper solution to prevent yield degradation due to particles produced during the LCD manufacturing process and a method for manufacturing a LCD using the same.
2. Discussion of the Related Art
With the rapid change in the information society, one of the information display device, a LCD module, gained its popularity because of the greater advantages, for example, miniaturization, lightweight, flatness, and low power consumption, as compared to a cathode ray tube (CRT). The CRT has advantages in its performance and price, however, size and portability of the CRT are not matched up with the LCD. While the LCD is actively replacing the CRT with its advantages, however, LCD is more expensive than the CRT.
The LCD includes an array substrate on which a thin film transistor (TFT) is arranged, and includes a color filter substrate on which R/G/B color filter layers are formed. The array substrate and the color filter substrate are pressed together with a liquid crystal layer interposed therebetween. The array substrate and the color filter substrate are manufactured through several mask processes. Specifically, the array substrate is manufactured through a 5-mask process.
A first mask process includes forming a gate bus line and a gate electrode on a transparent glass substrate by depositing a metal film on the transparent glass substrate, thereafter etching the deposited metal film. Subsequently, a second mask process includes forming a channel layer on the substrate by forming a gate insulating film, an amorphous silicon film, and a doped amorphous silicon film. Next, a third mask process includes forming source/drain electrodes and a data bus line by depositing source/drain metal films on the substrate having the channel layer formed thereon and then etching the deposited source/drain metal films. Then, a fourth mask process includes forming a protective film for device protection and then forming a contact hole. Finally, a fifth mask process includes forming a pixel electrode by depositing an indium tin oxide (ITO) transparent metal film on the substrate having the protective film formed thereon and then etching deposited ITO transparent metal film.
However, an increase in the total number of mask processes increases the LCD unit price. Accordingly, research for reducing the total number of mask processes has been conducted. As a result, a 4-mask process where the channel layer and the source/drain electrodes are simultaneous formed has been developed.
FIG. 1 is a plan view illustrating a pixel structure of a related art LCD. Referring to FIG. 1, a gate bus line 1 for applying a driving signal and a data bus line 3 for applying a data signal are vertically intersecting each other, whereby a unit pixel area is defined. A pixel electrode 9 is disposed in the unit pixel area. A TFT, acting as, a switching device is disposed on a region where the gate bus line 1 and the data bus line 3 intersect each other vertically. The TFT includes a gate electrode 5 electrically connected to the gate bus line 1, a channel layer formed on the gate electrode 5, and source/drain electrodes 7a and 7b. When the TFT is turned ON, a data signal from the data line 3 is applied through the source electrode 7a and the drain electrode 7b to the pixel electrode 9.
The data signal applied to the pixel electrode 9 forms an electric field in association with a common electrode, which rotates liquid crystal molecules in a liquid crystal layer to adjust the transmissivity of light passing through the liquid crystal layer. The adjusted light passes through the color filter layers of the color filter substrate, such that an image of various colors is displayed.
FIGS. 2A to 2D are cross-sectional views along line I-I′ of FIG. 1, illustrating a related art LCD manufacturing process of FIG. 1.
Referring to FIG. 2A, a metal film of Al or Cr is deposited on a transparent dielectric substrate 10 through a sputtering method. Accordingly, the gate bus line 1 and the gate electrode 5 are formed through a first mask process.
Referring to FIG. 2B, a gate insulating film 2 is formed on the dielectric substrate 10 and the gate electrode 5, thereafter an amorphous silicon film and an n+ amorphous silicon film are formed. Then, a metal film is deposited on the dielectric substrate 10 on which the n+ amorphous silicon film has been formed. Thereafter, the source/drain electrodes 7a and 7b, an ohmic contact layer 6, and a channel layer 4 are simultaneous formed through a second mask process by patterning a halftone photoresist film, and successively etching the metal film, the amorphous silicon film, and the n+ amorphous silicon film. The halftone photoresist film is patterned by using a diffractive exposure mask.
Referring to FIG. 2C, a protective film 11 is formed on a surface of the dielectric substrate 10 on which the source/drain electrodes 7a and 7b have been formed. Then, a contact hole is formed exposing the drain electrode 7B through a second mask process.
Referring to FIG. 2D, a transparent ITO metal film is deposited on the dielectric substrate 10 on which the contact hole has been formed. Then, the pixel electrode 9 is formed through a fourth mask process to complete the LCD manufacturing process. However, when compared with a 3-mask process that is being developed, the 4-mask process increases the LCD manufacturing cost because of the increased total number of individual mask processes.